Probe for a magnetic remanence measurement method, and method for detecting deposits of foreign material and inclusions in hollow spaces

ABSTRACT

A probe for a magnetic remanence measurement method, in particular for detecting foreign material deposits and inclusions in hollow spaces, the hollow spaces being formed in a non-ferromagnetic material and the foreign material deposits and inclusions being made of a ferromagnetic material, wherein the probe includes at least one magnetic field sensor, at least one first and one second magnet, the magnets being configured before the at least one magnetic field sensor in a direction of introduction into the hollow space, and being situated relative to one another in such a way that their pole axes run non-parallel to one another.

BACKGROUND

The present invention relates to a probe for a magnetic remanencemeasurement method, in particular for detecting deposits of foreignmaterial and inclusions in hollow spaces, the hollow spaces being formedin a non-ferromagnetic material, and the foreign material deposits andinclusions being made of a ferromagnetic material, and the probe havingat least one magnetic field sensor. The present invention furtherrelates to a method for detecting foreign material deposits andinclusions in hollow spaces, the hollow spaces being formed in anon-ferromagnetic material, and the foreign material deposits andinclusions being made of a ferromagnetic material.

In a large number of technical applications, significant problems arecaused by ferromagnetic inclusions situated in a non-ferromagneticsurrounding environment. Thus, for example, the smallest foreignmaterial deposits or inclusions in components of aircraft engines cancause significant damage to these engines. Corresponding foreignmaterial deposits and inclusions can be, for example, cutting materialresidue resulting from breakage or chipping of cutting edges of drillingtools. Such inclusions result in defects in the area of the surface ofthe corresponding components, but these defects are not easilyrecognizable. These foreign material deposits and inclusions becomeparticularly relevant in the case of drilled holes, because these havean increased level of tension and are also very difficult to access. Inorder to detect foreign material deposits and inclusions in hollowspaces, in particular in bores in turbines and compressor materials ofaircraft engines, destruction-free test methods based on ferromagnetismhave been described. These methods are applicable because the materialsspalled by the drilling tool are ferromagnetic hard metal, whereasturbine and compressor materials are not ferromagnetic. In particular,the magnetic remanence method, and also the eddy current method, havebeen described and used for the detection of small ferromagneticparticles in a non-ferromagnetic environment. However, these two methodshave various disadvantages when used for the detection, location, andcharacterization of ferromagnetic inclusions in hollow spaces. Thus, upto now it has been possible to carry out the magnetic remanence methodfor the detection of foreign material deposits and inclusions only fromthe surface of the component. On the other hand, hollow space testsusing the eddy current method have the disadvantage that it is possibleto distinguish ferromagnetic inclusions from geometric anomalies only toa limited extent.

Therefore, the object of the present invention is to provide a probe ofthe general type described for a magnetic remanence measurement methodthat enables reliable detection and location of ferromagnetic foreignmaterial deposits and inclusions in hollow spaces.

In addition, the object of the present invention is to provide a methodof the general type described for the detection of foreign materialdeposits and inclusions in hollow spaces that ensures a reliabledetection and location of ferromagnetic foreign material deposits andinclusions.

SUMMARY

A probe according to the present invention for a magnetic remanencemethod, in particular for detecting foreign material deposits andinclusions in hollow spaces, the hollow spaces being formed in anon-ferromagnetic material and the foreign material deposits andinclusions being made of a ferromagnetic material, has at least onemagnetic field sensor. In addition, the probe comprises at least onefirst and one second magnet, the magnets being configured before the atleast one magnetic field sensor in a direction of introduction into thehollow space, and being situated relative to one another in such a waythat their pole axes run non-parallel to one another. The arrangement oftwo magnets having pole axes that run differently results in amagnetization of the ferromagnetic foreign material deposits andinclusions in different directions, so that the main orientation of theforeign material particle or of the inclusion can be reliablyrepresented. Advantageously, the probe according to the presentinvention ensures a reliable detection and location of ferromagneticforeign material deposits and inclusions in hollow spaces. According toa specific embodiment of the probe according to the present invention,the pole axes of the first and second magnets can be situatedperpendicular to one another.

In further advantageous realizations of the probe according to thepresent invention, the magnetic field sensor and the magnets aresituated on a base element. The probe is advantageously configured suchthat it can be introduced into hollow spaces having a diameter between 2mm and 100 mm, in particular between 2 mm and 10 mm. The miniaturizationof the probe makes it possible to analyze even those hollow spaceshaving a very small diameter, such as hollow spaces resulting fromdrilling.

In a further advantageous realization of the probe according to thepresent invention, this probe has a first and a second magnetic fieldsensor, the first magnetic field sensor being fashioned for thedetection of a magnetic remanence caused by the first magnet, and thesecond magnetic field sensor being fashioned for the detection of amagnetic remanence caused by the second magnet. The first magnet can besituated between the first magnetic field sensor and the second magneticfield sensor, and the second magnet can be situated before the secondmagnetic field sensor, in the direction of introduction of the probeinto the hollow space. The allocation of a respective magnetic fieldsensor to each magnet makes it possible for magnetic remanences thatresult from the movement of the probe in the hollow space to be detectedimmediately by the corresponding magnetic field sensor. In this way,even inclusions having small diameters can be reliably detected.

In further advantageous realizations of the probe according to thepresent invention, the first and the second magnetic field sensor arewhat are known as GMR sensors (Giant MagnetoResistance sensors), or arewhat are known as AMR sensors (Anisotropic MagnetoResistance sensors).Such sensors have the advantage that they are normally small in theirdimensions, and, in their embodiments as gradiometers, are relativelyinsensitive to magnetic background signals. It is therefore possible tomeasure extremely weak magnetic fields such as those that arise due tothe magnetic remanence of the foreign material deposits and inclusions.

In another advantageous construction of the probe according to thepresent invention, the magnetic field sensor or sensors are connected toan evaluation unit. In this way, it is possible for example tographically display the determined measurement values, so that, besidesthe number of detected foreign material deposits and inclusions, theirnumber and position in the hollow space, or in the material surroundingthe hollow space, can be determined and displayed precisely.

In a further advantageous construction of the probe according to thepresent invention, the non-ferromagnetic material is a nickel-basedalloy or a titanium alloy. Ferromagnetic foreign material deposits andinclusions are made of hard metal, in particular tungsten carbide. Thenamed non-ferromagnetic materials are used in particular for themanufacture of components of compressors and turbines of aircraftengines. The named ferromagnetic foreign material deposits andinclusions arise during the spalling of parts of a drilling tool duringthe manufacture of drilled holes in the named components of the aircraftengines.

A method according to the present invention for detecting foreignmaterial deposits and inclusions in hollow spaces, the hollow spacesbeing formed in a non-ferromagnetic material and the foreign materialdeposits and/or inclusions being made of a ferromagnetic material, hasthe following steps:

a) introduction of a probe into the hollow space, the probe comprisingat least one magnetic field sensor and at least one first and one secondmagnet, the magnets being configured before at least one magnetic fieldsensor, in the direction of introduction into the hollow space, andsituated relative to one another such that their pole axes runnon-parallel to one another; b) magnetization of the foreign materialdeposits and inclusions using the magnets; c) measurement by themagnetic field sensor of the signatures of the magnetic fields, whichhave resulted from the magnetization and are measurable as magneticremanence after the magnets are further moved, of the foreign materialdeposits and inclusions; and d) evaluation of the measured magneticfield data and presentation of the number and position of the foreignmaterial deposits and inclusions in the hollow space. Through themagnetization of the ferromagnetic foreign material particles and/orinclusions in various directions, it is possible to precisely determinethe main orientation of the particle or of the inclusion. Thus, areliable detection and location of ferromagnetic foreign materialdeposits and/or inclusions is ensured.

In an advantageous realization of the method according to the presentinvention, the probe has a first and a second magnetic field sensor, thefirst magnetic field sensor being fashioned for the detection of amagnetic remanence caused by the first magnet, and the second magneticfield sensor being fashioned for the detection of a magnetic remanencecaused by the second magnet. The first magnet can be situated betweenthe first magnetic field sensor and the second magnetic field sensor,and the second magnet can be situated in the hollow space before thesecond magnetic field sensor, in the direction of introduction of theprobe. In addition, the pole axes of the first and second magnets can besituated perpendicular to one another. Such an arrangement ensures thateven the smallest ferromagnetic foreign material deposits and inclusionscan be reliably detected, because the magnetic field sensors measure themagnetic field produced by the magnetic remanence immediately after themagnetization of these particles and inclusions. In particular, it isalso possible to determine precisely the sizes and locations of theparticles and inclusions.

In another advantageous realization of the method according to thepresent invention, the probe is configured such that it can beintroduced into a hollow space having a director between 2 mm and 100mm, in particular between 2 mm and 10 mm. Through the miniaturizationaccording to the present invention of the probe, it is possible todetect ferromagnetic foreign material deposits and inclusions even inbored holes having corresponding diameters. Here, the first and secondmagnetic field sensor can be what are known as GMR sensors or what areknown as AMR sensors, which on the one hand can be fashioned with smalldimensions, and on the other hand are relatively insensitive to possiblemagnetic disturbance or interference effects.

In another advantageous realization of the method according to thepresent invention, inside the hollow space the probe is moved along astraight line or is rotated. This makes it possible in one working stepalso to detect and display three-dimensional distribution patterns offerromagnetic foreign material deposits and inclusions in the hollowspaces.

The probe according to the present invention described above or themethod according to the present invention described above are used inthe detection of foreign material deposits and inclusions in bored holesin components of aircraft engines, in particular in compressor andturbine components. The foreign material deposits and inclusions can beparticles spalled from drilling tools, made of ferromagnetic materials.In this way, in this sensitive technical area it is possible to avoiddamages caused for example by the hard metal inclusions, remaining inthe bored hole, of the material spalled from the drilling tool. Thisrelates on the one hand to damages that can occur duringpost-processing, for example using various frictional methods, as wellas to later damage, such as for example the formation of cracks in thecorresponding engine components.

In an advantageous realization, the probe is moved in linear fashioninside the hollow space.

The magnetic field sensor or sensors are preferably magnetic fieldgradiometers.

BRIEF DESCRIPTION OF DRAWINGS

Further advantages, features, and details of the present inventionresult from the following description of a graphically depictedexemplary embodiment.

FIG. 1 shows a representation of a probe according to the presentinvention for a magnetic remanence measurement method; and

FIG. 2 shows a screen print of a measurement result of two GMR magneticfield sensors of the probe according to FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows a probe 10 for use in a magnetic remanence measurementmethod. Probe 10 consists of an elongated base element 12 on which thereare situated a first magnet 18 and a second magnet 20, as well as afirst magnetic field sensor 14 and a second magnetic field sensor 16. Inaddition, various terminals 34 are formed on base element 12, such asfor example terminals for the supply of power to magnetic field sensors14, 16, terminals for the grounding of magnetic field sensors 14, 16,and also terminals for the data transmission of the values determined bymagnetic field sensors 14, 16 to an evaluation unit (not shown). It canbe seen that in the direction of introduction of sensor 10 into a hollowspace 30 of a component 32 made of non-ferromagnetic material, secondmagnet 20 is situated before second magnetic field sensor 16, and secondmagnetic field sensor 16 is situated before first magnet 18, and firstmagnetic field sensor 14 is situated behind first magnet 18. Here, thedistance between second magnet 20 and second magnetic field sensor 16can be approximately 2 mm, the distance between first magnet 18 andfirst magnetic field sensor 14 can be approximately 3 mm, and thedistance between magnetic field sensors 14, 16 can be approximately 15mm. In the depicted exemplary embodiment, magnetic field sensors 14, 16are approximately 1.3 mm high. Magnets 18, 20 have a height ofapproximately 1 mm. In addition, it can be seen that pole axes 22, 24 offirst magnet 18 and of second magnet 20 run in different directions; inthe depicted exemplary embodiment, they run perpendicular to oneanother. The pole axis 24 of second magnet 20 is situated perpendicularto sensitivity axes 26, 28 of magnetic field sensors 14, 16. Pole axis22 of first magnet 18 is correspondingly oriented parallel tosensitivity axes 26, 28. Overall, probe 10 is dimensioned in such a waythat it can be introduced into a hollow space 30 that has a diameterbetween 2 mm and 100 mm, in particular between 2 mm and 10 mm. Hollowspace 30 shown in the exemplary embodiment has a diameter ofapproximately 7.2 mm. Base element 12 is made of a non-ferromagneticmaterial.

Magnetic field sensors 14, 16 used in the exemplary embodiment are whatare known as GMR sensors (Giant MagnetoResistance sensors). These arecapable of detecting very small flux densities or magnetic fields ofmagnetized ferromagnetic foreign material deposits and inclusions.

FIG. 2 shows a screen print of a measurement result of the two GMRmagnetic field sensors 14, 16 of probe 10 constructed according to theexemplary embodiment shown in FIG. 1. This is a line scan of the twomagnetic field sensors 14, 16. The Figure clearly shows the peaks ofrelatively high magnetic flux density in certain areas of the linearscan, each peak representing a ferromagnetic inclusion in hollow space30. This is a bipolar representation, in which changes in the magneticflux density are indicated in millivolts and are shown proportional tothe measured magnetic flux density in teslas (cf. the centricallyoriented vertical axis of the diagram). The depicted linear scan showsclearly that the arrangement of two magnets 18, 20 whose pole axes 22,24 are oriented differently to one another, in particular perpendicularto one another, enables a very precise detection of foreign materialdeposits and inclusions in hollow spaces 30, with respect both to theirnumber and to their size and positioning inside hollow space 30.

1. A probe for detecting foreign material deposits and inclusions inhollow spaces, the hollow spaces being formed in a non-ferromagneticmaterial and the foreign material deposits and inclusions being made ofa ferromagnetic material, the probe comprising: at least one magneticfield sensor, at least one first and one second magnet, the magnetsbeing positioned before the at least one magnetic field sensor in adirection of introduction into the hollow space, and being situatedrelative to one another so that their pole axes are non-parallel.
 2. Theprobe as recited in claim 1, wherein the magnetic field sensor and themagnets are situated on a base element.
 3. The probe as recited in claim1, wherein the probe has a first and a second magnetic field sensor, thefirst magnetic field sensor configured to detect a magnetic remanencecaused by the first magnet, and the second magnetic field sensorconfigured to detect a magnetic remanence caused by the second magnet.4. The probe as recited in claim 3, wherein the first magnet is situatedbetween the first magnetic field sensor and the second magnetic fieldsensor, and the second magnet is situated before the second magneticfield sensor in the direction of introduction of the probe into thehollow space.
 5. The probe as recited in claim 1, wherein the probe isdimensioned such that the pole axes of the first and second magnet areperpendicular to one another.
 6. The probe as recited in claim 1,wherein said probe is configured to fit within hollow spaces having adiameter between 2 mm and 100 mm.
 7. The probe as recited in claim 3,wherein the first and the second magnetic field sensors are one of GMRsensors (Giant MagnetoResistance sensors) and AMR sensors (AnisotropidMagnetoResistance sensors).
 8. The probe as recited in claim 1, whereinthe at least one magnetic field sensor is connected to an evaluationunit.
 9. The probe as recited in claim 1, wherein the non-ferromagneticmaterial is one of a nickel-based alloy and a titanium alloy, and theferromagnetic foreign material deposits and inclusions are made oftungsten carbide.
 10. A method for detecting foreign material depositsand inclusions in hollow spaces, the hollow spaces being formed in anon-ferromagnetic material, and the foreign material deposits andinclusions being made of a ferromagnetic material, comprising: a)introduction of a probe into the hollow space, the probe comprising atleast one magnetic field sensor and at least one first and one secondmagnet, the magnets being configured before at least one magnetic fieldsensor in the direction of introduction into the hollow space, and beingsituated relative to one another such that their pole axes runnon-parallel to one another; b) magnetization of the foreign materialdeposits and inclusions by the magnets; c) measurement by the magneticfield sensor of the signatures of the magnetic fields of the foreignmaterial deposits and inclusions, said signatures resulting from themagnetization and being measurable as magnetic remanence after furthermovement of the magnets; and d) evaluation of the measured magneticfield data and representation of the number and position of the foreignmaterial deposits and inclusions in the hollow space.
 11. The method asrecited in claim 10, wherein the probe has a first and a second magneticfield sensor, the first magnetic field sensor being fashioned for thedetection of a magnetic remanence caused by the first magnet, and thesecond magnetic field sensor being fashioned for the detection of amagnetic remanence caused by the second magnet.
 12. The method asrecited in claim 11, wherein the first magnet is situated between thefirst magnetic field sensor and the second magnetic field sensor, andthe second magnet is situated before the second magnetic field sensor inthe direction of introduction of the probe into the hollow space. 13.The method as recited in claim 10, wherein the pole axes of the firstand second magnets are situated perpendicular to one another.
 14. Themethod as recited in claim 10, wherein the probe is dimensioned suchthat it can be introduced into a hollow space having a diameter between2 mm and 100 mm.
 15. The method as recited in claim 10, wherein thefirst and the second magnetic field sensors are GMR sensors (GiantMagnetoResistance sensors) or AMR sensors (Anisotropic MagnetoResistancesensors).
 16. The method as recited in claim 10, wherein the probe isrotated inside the hollow space.
 17. The method as recited in claim 10,for the detection of foreign material deposits and inclusions in boredholes in components of aircraft engines.
 18. The use of a probe asrecited in claim 1, for the detection of foreign material deposits andinclusions in bored holes in components of aircraft engines.
 19. The useof a probe as recited in claim 18, wherein the foreign material depositsand inclusions are spalled fragments from drilling tools, made offerromagnetic materials.